Do you know what size tyres your car needs?

Knowing the size of your tyres can be really helpful in many situations. Perhaps you’re due a tyre change, and want to price up some options online. Or maybe a tyre has blown out on the roadside, and you need to let your recovery service or breakdown support know what size tyre replacement you’re going to need.

While many of us may not know the size of our tyres off of the top of our heads, being able to find this information when you’re in a situation where the pressure’s on is important. That’s why we’ve put together some information to help you find out what size tyres your car uses.

How can I find out my tyre size?

There are a few different ways to find out the size of your tyres. One of the easiest ways is to look at the tyres themselves. You can find out the size by looking at the tyre sidewall; you’ll find a series of letters and numbers, and deciphering them will tell you what size you need.

The first set of numbers indicates the width of the tyre, in millimeters. For example, 175mm or 205mm.

Next, you’ll find two numbers that tell you the profile of the tyre, displayed as a percentage of the total tyre width. For example, 55 - so 55%.

Third, comes wheel size. This is made up of two parts - a letter, detailing the tyre construction. Most of the time, this letter will be an ‘R’, meaning radial ply construction. This will be followed by a number, which represents the rim diameter. For example, you might see R16 or R17.

Finally, you’ll see a speed rating. Once again, this is made up of two parts - the load index, and the speed symbol. The speed symbol is particularly important, and it needs to relate to the speed of the car. For example, having a low speed rated tyre on a very fast car would put the tyres in a position where they don’t operate effectively - which could be very dangerous.

You can find out more about reading tyre markings in our handy guide.

Why is having the right size tyres important?

Having the right size and rating of tyre on your car is important in keeping you and other road users safe. Factors like speed, longevity, heat resistance, and wear and tear are all considered when tyres are selected for a car during manufacturing - which is why these standards must be maintained.

Not only could it prove unsafe to fit tyres of a different specification to your car, but you could, in some serious situations, even invalidate your insurance policy. Particularly if you’re unfortunate enough to be in a road traffic collision caused in part by the change in tyres.

Replacing your tyres

If you’re not sure what size tyres you need, or you’re looking for some advice on whether your tyres need replacing, head down to your local Tyre Pros centre. Our friendly teams will be happy to advise you on the best tyres for your car.